For certain groups of mushrooms, taste or smell can be diagnostic characters. In most cases, these tests are used to identify a species within a genus. So, of course, you must have already identified your unknown down to the genus level.
While it may seem that odor and taste would be minor tests that can be skipped, quite the opposite is true for certain genera. In fact, for groups such as Agaricus, Russulaceae, and boletes, these characters are critical in determining edibility.
Odors
Mushroom tissues are filled with complex organic compounds that typically exibit unique characters of the fungus' peculiar metabolism. In some cases, these compounds exude characteristic aromas that can be used as a diagnostic tool.
When checking for odors, it is often necessary to cut or crush the flesh to release compounds contained in the tissues. Old or dry mushrooms may have lost their aromas, so it is important to find recently matured specimens.Phenolic vs. Almond scent
The process of determining edibility in the genus Agaricus typically involves both a bruising color check and a scent test. The color test is mentioned in the Tissue and Color Change section.
A phenol aroma, similar to the smell or ink or fresh asphalt, indicates the presence of a poisonous compound present in some Agaricus such as A. xanthodermus.
Conversely, several highly prized edible Agaricus species exude an almond scent when their flesh is crushed. This is true of A. absolutens and A. augustus, both excellent edibles.
Agaricus xanthodermus, a poisonous mushroom with characteristic phenolic smell. Photo: see stamp.
Anise aroma
A few mushrooms have a distinct anise aroma, owing to the presence of anisaldehyde, the same compound found in anise. The most commonly noted anise mushroom is Clitocybe odora. One other mushroom with an anise-like aroma is Cortinarius odorifer (featured photo), which I have found in eastern Arizona.
Cortinarius odorifer, with a distinct anise aroma.
Tastes
Just as various aromas can indicate the presence of a particular fungal metabolite, taste testing certain mushrooms is another method for detecting active compounds.
To taste test a mushroom, a tiny portion of the cap is bitten off, including a portion of the pellicle (cap surface), the gills, and the tissues inbetween. The flesh should be crushed with your front teeth, allowed to sit on the tongue for a few seconds, then spit out. You are not searching so much for flavor, as for a reaction, which may take time to develop. Typically, the sensations you are checking for are pepperiness and bitterness.Peppery sensation
Detecting a peppery sensation is a key identification diagnostic for members of Russula and Lactarius. As a general rule, peppery members of Russulaceae are either poisonous or inedible.
Pepperiness between species can be a subtle thing. For some, the sensation is immediate and potent. For others, the sensation can take several seconds to manifest.
Russula sp. Many Russulas have a fierce peppery taste.
Bitter taste
Bitterness tests are suggested for many different mushroom groups, and typically bitterness indicates inedibility. Often it is necessary to narrow down the identity of your unknown mushroom to a particular genus or species group in order for the bitterness test to be diagnostic.
One group for which the bitterness test is particularly useful is the boletes. As a general rule, boletes with red pores and / or a bitter taste are not edible. Personally, I have only encountered one species of bitter bolete, Tylopilus felleus, and its powerful bitteriness is inescapeable.
Tylopilus felleus, a bitter bolete.
Photo: see stamp
Sweet taste
There is one particular mushroom that I wanted to include for its sweet taste. It is Clavariadelphus truncatus, the sweet club. This mushroom (a stretch of the word) is closely related to the coral genus Clavaria, but appears all by itself as one large flat topped club. Its sweet taste is due to sugar alcohol mannitol, which can act as a laxitive if too many are eaten. I have found only one of these in eastern Arizona, and it was indeed very sweet and tasty!
Clavariadelphus truncatus, the sweet club.